a. Field of the Invention
The present invention pertains generally to disk storage systems and specifically to disk storage systems with provisions for disaster recovery.
b. Description of the Background
Redundant arrays of independent disks (RAID) is standardized technology for the storage of data with emphasis on performance, fault tolerance, and the ability to recover data due to a failure of a disk drive. Many RAID products are commercially available.
The RAID Advisory Board of St. Peter, Minn. has defined and standardized several different RAID levels. RAID level 1 (‘RAID 1’), for example, is a mirrored disk wherein a complete copy of the data on one disk is simultaneously maintained and stored on a second disk. In the event of a failure of one disk, a complete copy of the data on the second disk is available. The data on the second disk may be used to recreate the data on the first disk when the first disk is replaced or repaired. RAID 5 uses several disks to store data in stripes for read and write speed. RAID 5 also incorporates parity data recovery method for tolerating the failure of a complete disk drive in the system.
Hot spare disks may be present in a RAID storage system. A hot spare disk is one that is capable of being used, but sits idle until one of the disks in a RAID system need to be replaced.
The existing technology addresses the need for disaster recovery from errors in the disk drives such as media problems, disk crashes, noisy communications, and other problems that may destroy data or prohibit data access. However, the RAID technology does not address problems such as virus attacks, unintentional deletion of files, and other forms of data corruption where a backup system is required to restore the system to operation. For example, a virus attack may cripple a computer, wiping out files and data that are essential for the functioning of the computer. The only alternative for a system administrator may be to reinstall essential operating software and data from a back up. Such operations may take several hours to complete, leaving an otherwise essential computer out of service for a substantial amount of time.
It would therefore be advantageous to provide a system and method for recovering from data corruption problems quickly and with a minimum of data loss. Further it would be advantageous if the backup system used elements of existing RAID technologies.